Method of processing resist onto substrate and resist processing apparatus

ABSTRACT

A method of forming a resist on a substrate and processing the resist in a resist processing system having a processing region and a non-processing region which are air-conditioned, the method comprising the steps of, transferring the substrate into the non-processing region, coating the resist on the substrate, exposing the coated resist, developing the exposed resist, subjecting the coated resist at least once, to heat treatment in a period from the transferring step to the developing step, detecting at least once, the concentration of an alkaline component which causes defective resolution of the resist in a processing atmosphere in a period from the transferring step to the developing step, setting a threshold value for the concentration of the alkaline component in the processing atmosphere which causes the defective resolution of the resist, and controlling and changing at least one processing atmosphere in the steps in accordance with a detected concentration of the alkaline component and the threshold value.

This application is a Division of application Ser. No. 08/823,470 Filedon Mar. 24, 1997 U.S. Pat. No. 5,932,380.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of processing a resist onto asubstrate such that a photoresist is coated with a substrate such as asemiconductor wafer and then the coated photoresist is exposed anddeveloped, and to a resist processing apparatus.

2. Discussion of the Background

As the density of electric devices mounted on a substrate has beenrapidly raised, the photolithography technology has been improvedenergetically. For example, a process for manufacturing 64 MDRAM or 256MDRAM has been performed such that a chemically amplified resist is usedin place of the conventional novolac system photoresist.

If the chemically amplified resist is exposed to light, acid generatedfrom the sensitive material is diffused due to heating process to act ona catalyst, thus causing base resin to be decomposed or causing themolecular structure of the base resin to be changed. It leads to a factthat the base resin is made to be soluble or insoluble with respect tothe developer.

Since one molecule of the catalyst of the chemically amplified resistcontributes to a plurality of chemical reactions, higherphotosensitivity is realized as compared with conventional resists.Moreover, the chemically amplified resist, having a high lighttransmittance in a short wavelength region, is able to relax the lightintensity distribution in the direction of the thickness of the filmeven if an eximer laser beam having a short exposing wavelength is used.Thus, line widths of a level of 0.3 mm can be realized when a circuitpattern is formed.

However, the chemically amplified resist, depending on the environmentby a degree greater than the conventional resists, has a risk thatorganic amine, such as ammonia and NMP (N-methyl.2 pyrrolidinone), andtheir polar materials (hereinafter simply called as "alkalinecomponents"), each existing in the processing atmosphere in a smallquantity, and the chemically amplified resist cause neutralizationreactions to take place and thus the resist is devitalized. If theresist is devitalized, accurate line widths of a highly-integratedcircuit pattern cannot be realized in the developing process. Thus, aso-called defective resolution takes place.

The inventors of the present invention have developed and researched theforegoing problem, thus resulting in consideration being performed suchthat the following three facts relate to the alkaline component which ismixed in the processing atmosphere. First, use of a solution containingammonia as washing liquid for removing particles allowed to adhere tonon-processed wafer causes alkaline component to be generated in theprocessing atmosphere. A second fact is such that use ofhexamethyldisilazane (HMDS) in the adhesion process which is performedbefore the resist is applied causes the alkaline component to begenerated in the processing atmosphere. A third fact is that a processfor forming a reflection preventive film on the surface of the wafer byusing amine solvent results in the alkaline component being generated inthe processing atmosphere.

In U.S. Pat. No. 5,434,644, a resist processing apparatus has beendisclosed which comprises a special chemical filter capable of removingalkaline component in the resist processing atmosphere. The element ofthe chemical filter is impregnated with acid components, such asphosphoric acid, so as to remove the alkaline component attributable tothe neutralizing reaction with the acid component so that clean downflowair is introduced into a processing portion. If the foregoing apparatusis used for a long time, and thus the filter element deterioratescausing the removal performance also deteriorates, the filter elementmust be changed at proper timing because the concentration of thealkaline component in the processing atmosphere is raised gradually.

Hitherto, an operator of the apparatus samples each point of theinternal atmosphere in each apparatus. Then, the concentration of thealkaline component included in each sample is analyzed. In accordancewith a result of the analysis, the filter element is changed. However,the conventional method takes an excessively long time to obtain theresult of the detection of the alkali concentration. Thus, a quickcountermeasure against the rise in the concentration of the alkalinecomponent in the processing atmosphere cannot be taken. Therefore, themanufacturing yield cannot be improved and the reliability of theapparatus has been unsatisfactory.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of processinga resist onto a substrate and a resist processing apparatus capable ofraising manufacturing yield of semiconductor devices having ahighly-integrated circuit pattern and improving the reliability of theapparatus.

According to one aspect of the present invention, there is provided amethod of processing a resist onto a substrate such that the substrateis subjected to a resist process in a resist processing system having aprocessing region and a non-processing region which are air-conditioned,the method of processing a resist onto a substrate comprising:

(a) a step for transferring the substrate into the non-processingregion;

(b) a step for coating the resist with the substrate;

(c) a step for exposing the coated resist;

(d) a step for developing the exposed resist;

(e) a step for, at least once, subjecting the coated resist to heattreatment in a period from the step (a) to the step (d);

(f) a step for, at least once, detecting the concentration of analkaline component which causes defective resolution of the resist in aprocessing atmosphere in a period from the step (a) to the step (d);

(g) a step for setting a threshold value for the concentration of thealkaline component in the processing atmosphere which causes thedefective resolution of the resist; and

(h) a step for controlling and changing at least one processingatmosphere in the steps (a) to (e) in accordance with a detected valuein the step (f) and the threshold value in the step (g).

According to another aspect of the present invention, there is provideda method of processing a resist onto a substrate such that the substrateis subjected to a resist process in a resist processing system having aprocessing region and a non-processing region which are air-conditioned,the method of processing a resist onto a substrate comprising:

(A) a step for transferring the substrate into the non-processingregion;

(B) a step for, in the processing region, coating the resist with thesubstrate;

(C) a step for, in the processing region, exposing the coated resist;

(D) a step for, in the processing region, developing the exposed resist;

(E) a step for, at least once, subjecting the coated resist to heattreatment in a period from the step (A) to the step (D);

(F) a step for, at least once, detecting the concentration of analkaline component which causes defective resolution of the resist in aprocessing atmosphere in a period from the step (A) to the step (D);

(G) a step for detecting the concentration of an alkaline componentcontained in an atmosphere of an external environment of the resistprocessing system;

(H) a step for setting a threshold value for the concentration of analkaline component in the processing atmosphere which causes thedefective resolution of the resist;

(I) a step for setting a threshold value of the concentration of thealkaline component contained in the atmosphere of the externalenvironment which causes defective resolution of the resist;

(J) a step for controlling and changing at least one processingatmosphere in the steps (A) to (E) in accordance with a detected valuein the step (F) and the threshold value in the step (H); and

(K) a step for controlling and changing the atmosphere of the externalenvironment of the resist processing system in accordance with adetected value in the step (G) and the threshold value in the step (I).

According to another aspect of the present invention, there is provideda resist processing apparatus having a processing region and anon-processing region which are air-conditioned, the resist processingapparatus comprising:

a resist coating portion for coating the resist with a substrate;

a heating portion for heating the substrate subjected to an exposingprocess;

a cooling portion for cooling the substrate;

a developing portion for developing the substrate;

an interface portion for transferring/receiving the substrate which hasbeen subjected to the exposing process;

means for transferring the substrate between the interface portion andeach of the resist coating portion, the heating portion, the coolingportion and the developing portion;

means for supplying downflow air to the processing region;

filter means disposed at least above the processing region and arrangedto remove an alkaline component contained in downflow air to beintroduced into the processing region, the filter means having anelement containing an acid component for reacting with the alkalinecomponent to capture the alkaline component;

concentration detection means for detecting the concentration of analkaline component existing in at least one atmosphere in the resistcoating portion, the developing portion, the heating portion, thecooling portion and the interface portion;

means for setting a threshold value of the concentration of the alkalinecomponent in the processing atmosphere which causes defective resolutionof the resist;

means for controlling at least one processing atmosphere in the resistcoating portion, the heating portion, the cooling portion and thedeveloping portion in accordance with the set threshold value and thedetected value; and

display means for receiving a signal from the control means to displaythe detected value.

According to another aspect of the present invention, there is provideda resist processing apparatus having a processing region and anon-processing region which are air-conditioned, the resist processingapparatus comprising:

a resist coating portion for coating the resist with the substrate;

a heating portion for heating the substrate subjected to an exposingprocess;

a cooling portion for cooling the substrate;

a developing portion for developing the substrate;

an interface portion for transferring/receiving the substrate which hasbeen subjected to the exposing process;

means for transferring the substrate between the interface portion andeach of the resist coating portion, the heating portion, the coolingportion and the developing portion;

means for supplying downflow air to the processing region;

filter means disposed at least above the processing region and arrangedto remove an alkaline component contained in downflow air to beintroduced into the processing region;

means for setting a threshold value of the concentration of the alkalinecomponent in the processing atmosphere which causes defective resolutionof the resist;

first concentration detection means for detecting the concentration ofthe alkaline component existing in at least one atmosphere of the resistcoating portion, the developing portion, the heating portion, thecooling portion and the interface portion:

second concentration detection means for detecting the concentration ofthe alkaline component existing in the atmosphere of an externalenvironment of the resist processing system;

control means for controlling and changing at least one atmosphere inthe resist coating portion, the developing portion, the heating portion,the cooling portion and the interface portion in accordance with valuesdetected by the first and second concentration detection means and theset threshold value; and

display means for receiving a signal from the control means to displaythe detected values.

According to the present invention, the concentration of the alkalinecomponent in the processing atmosphere for the substrate is detected,and then the detected value is compared with the threshold value.Therefore, the processing atmosphere can be controlled in an onlinemanner. Moreover, a value which is the same or lower than the thresholdvalue is displayed and whether or not the operation for processing thesubstrate is continued is determined. Then, a state of the atmosphere inthe processing portion can be notified to an operator. Therefore, damageof the resist can be prevented satisfactorily.

The wafer applied with the resist and exposed to light was allowed tostand in an atmosphere in which the concentration of ammonia was about 1ppb and in an atmosphere in which the concentration of the same wasabout 10 ppb. A required width of lines of the pattern of ±0.3% wassatisfied in the former atmosphere (alkali concentration of 1 ppb).However, the pattern was deformed excessively in the latter atmosphere(alkali concentration of 10 ppb).

The chemically amplified resist can be selected from IX-60 (trade markof Japan Synthetic Rubber), APEX-E (trade mark of IBM), AZ-DX46 (trademark of HOECHST) and AXT-248 (trade mark of Seapley) etc;

The filter element may be impregnated with the acid component, such asphosphoric acid and sulfonic acid.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe invention, and together with the general description given above andthe detailed description of the preferred embodiments given below, serveto explain the principles of the invention.

FIG. 1 is a schematic plan view showing a semiconductor wafer resistapplying/developing system;

FIG. 2 is a cross sectional block diagram of a resist applying portionhaving a resist processing apparatus for substrates according to anembodiment of the present invention;

FIG. 3A is a flow chart of a method of resist-processing a substrateaccording to the embodiment of the present invention;

FIG. 3B is a flow chart of the ensuing portion of the method ofresist-processing the substrate according to the embodiment of thepresent invention;

FIG. 4 is a block diagram schematically showing an apparatus accordingto another embodiment;

FIG. 5 is a cross sectional block diagram schematically showing theresist applying portion having the apparatus for resist-processing asubstrate according to the embodiment of the present invention;

FIG. 6 is a perspective view showing the shape of a resist processingsystem;

FIG. 7 is a plan view showing the resist processing system;

FIG. 8 is an exploded perspective view showing a case for a first filterand an element of the first filter; and

FIG. 9 is a horizontal cross sectional view showing the element of thefirst filter.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, preferred embodiments of the presentinvention will now be described.

As shown in FIG. 1, a resist processing system includes a cassettestation 4, a coating section 10, an interface section 30 and an exposingsection 40. The cassette station 4 has a wafer moving mechanism 2 and aholder 3. A first cassette 1a for accommodating non-processed wafer Wand a second cassette 1b for accommodating a processed wafer aredisposed on the holder 3 at predetermined positions. The wafer movingmechanism 2 takes out the non-processed wafer W from the first cassette1a to store a processed wafer in the second cassette 1b.

The processing section has a plurality of the processing sections 10 to15 and 20 to 22 and a main conveying machine 6. The main conveyingmachine 6 is capable of running on a straight central passage 5 in theprocessing section, the main conveying machine 6 having an arm 7 forholding and moving the wafer W. The arm 7 is able to move in thedirections of the X, Y and Z axes and rotate around the Z axis by anangular degree of θ.

On one side of the central passage 5, there are formed non-heatprocessing sections 10, 15a, 15b, 20 and 22. On the other side of thecentral passage 5, there are formed heat processing sections 11, 12, 13and 21. The coating section 10 is formed adjacent to the cassettestation 4 and having two resist coating units 15a and 15b. The resistcoating unit 15a applies a reflection protective film to the wafer W,while the resist coating unit 15b applies photoresist to the wafer W.The developing section 20 is formed adjacent to the interface section 30and has two developing units 22. Each of the developing units 22develops the wafer W subjected to the exposing process in an exposingunit 40.

The scrubbing unit 11 scrub-cleans the wafer W with rotating brushes. Anadhesion processing unit 12a subjects the surface of the wafer W to ahydrophobic process using hexamethyldisilazane (HMDS). The processingatmosphere of the adhesion processing unit 12a usually includes alkalinecomponent at a concentration of 4 ppb to 50 ppb. A cooling unit 12bcools the wafer W. Baking units 13 and 21 heat the wafer W to which theresist has been applied. A jet-water cleaning unit 14 cleans the wafer Wwith jet stream of pure water. As shown in FIG. 2, the baking unit 13has hot plates disposed vertically. A plurality of the adhesionprocessing units 12a and the cooling units 12b are formed in theprocessing unit 12.

The interface unit 30 is formed adjacent to the developing unit 20 andthe baking unit 21 in the processing section. The interface unit 30 hasa holder 31 for transferring/receiving the wafer W. The exposing unit 40is connected to the processing section through the interface unit 30.The exposing unit 40 has an exposing stage 41, two loading mechanisms 42and 44 and a cassette station on which the cassettes 43 are placed.

The side portions of the coating unit 10 and the developing unit 20 arecovered with a cover 81. The upper portion of the coating unit 10 andthe developing unit 20 are covered with a cover 82. The upper cover 82has an opening through which air is supplied from a common duct (notshown) of the plant into an air intake opening of each air cleaningmechanism 80. The air cleaning mechanism 80 is disposed above each ofthe processing sections 10 and 20 and the interface section 30.

As shown in FIG. 2, a duct 83 is formed in the uppermost portion of theair cleaning mechanism 80. A communication passage 84 for connecting theduct 83 to the processing units 15a and 15b has, in the downwarddirection, a chemical filter 85, an air blowing fan 86 and an ULPAfilter 87. Moreover, another ULPA filter 87a is formed above the resistcoating units 15a and 15b. The chemical filter 85 is operated to removethe alkaline component, while the ULPA filters 87 and 87a are operatedto remove particles. The number of the ULPA filters 87 may be two as isemployed in this embodiment or one.

An air-discharge passage 88 is formed in the floor portion of thecentral passage 5, the air-discharge passage 88 including an exhaust fan89. Thus, a downflow of air is formed from the air cleaning mechanism 80to the air-discharge passage 88. The air-discharge passage 88 is allowedto communicate with a circulating circuit (not shown) having an alkalinecomponent removing apparatus (not shown). The alkaline component in theexhaust air is removed by the alkaline component removal apparatus, andthen regenerated air is again supplied to the air cleaning mechanism 80through the circulating circuit.

Another air cleaning mechanism 80 is provided for the interface section30 so as to supply fresh air into the interface section 30. Air which issupplied to the air cleaning mechanism 80 satisfies a concentration ofthe alkaline component of 10 ppb or lower, which is the requirement forthe interior atmosphere of the clean room 90. The concentration of thealkaline component in supplied air 280 (See FIGS. 8 and 9) is lowered to1 ppb or lower after it has passed through the air cleaning mechanism80.

Each of the coating section 10, the developing section 20 and theinterface section 30 has an alkaline concentration analyzer 50. As shownin FIG. 2, a detection terminal 53 of the concentration analyzer 50 isdisposed in the upper space of each of the sections 10, 20 and 30 todetect the concentration of the alkaline component contained in airimmediately after blown out from the filter unit 80. The "alkalinecomponent" to be detected is organic amine, such as ammonia and NMP(N-methyl.2 pyrrolidinone), and their polar molecule components.

The alkaline concentration analyzer 50 may be ion chromatography. Forexample, a diffusion scrubber (not shown) and an auto-exchanger (notshown) are attached to the concentration analyzer 50.

As shown in FIG. 2, a tank 52 of the alkaline concentration analyzer 50accommodates pure water 51. An end of a sampling pipe 54 is submerged inpure water 51 in the concentration analyzer 50. Another end (detectionterminal) 53 of the sampling pipe 54 is disposed above the resistcoating units 15a and 15b and directly under the air blow-out opening ofthe air cleaning mechanism 80. An exhaust pipe 55 is submerged in purewater 51 in the concentration analyzer 50.

Detection signals output from the alkaline concentration analyzer 50 aresequentially supplied to an input portion of a CPU 60. A memory portionof the CPU 60 previously stores a predetermined threshold value. In thisembodiment, the threshold value of the concentration of the alkalinecomponent is determined to be 1 ppb.

An output portion of the CPU 60 is connected to a monitor 70 and analarm system 71. The alkaline concentration detected in each portion isdisplayed on the screen of the monitor 70 so that an operator of thesystem is permitted to immediately recognize the state of the system. Ifany one of the detected concentrations exceeds the threshold value, theCPU 60 operates the alarm system 71 to issue an alarm. If the thresholdvalue is set to be lower than 1 ppb (for example, 0.7 ppb), a chemicalfilter 85 can be changed prior to occurrence of defective resolutionwith sufficient time margin.

The CPU 60 feedback-controls the conveying machine 6 of the coating unit10 and a drive motor 17 of a spin chuck 16. In accordance with a programtransferred from the CPU 60, the process can be continued orinterrupted.

Referring to flow charts shown in FIGS. 3A and 3B, an operation of theforegoing apparatus to process the wafer W will now be described.

Initially, the wafer moving mechanism 2 takes out a non-processed waferW from the first cassette 1a of the cassette station 4 in aloader/unloader section, and then places the non-processed wafer W onthe holder 3 while centering the wafer W. The main conveying machine 6picks up the wafer W from the holder 3 by the arm 7 and holds the sameto introduce the wafer W into the processing section (step S1). Then,the main conveying machine 6 introduces the wafer W into the baking unit13 to pre-bake the wafer W in accordance with a predetermined recipe(step S2).

The wafer W is scrubbed with a brush in the scrubbing unit 11 (step S3),and then the wafer W is cleaned with jet water in the jet-water cleaningunit 14 (step S4). While heating the wafer W, the wafer W is subjectedto an adhesion process in the adhesion processing unit 12a (step S5). Analkaline component generated due to the adhesion process is brought tothe air-discharge passage 88 in the floor portion by the downflow air.Then, the alkaline component is absorbed and removed by an alkalinecomponent absorbing apparatus (not shown) disposed in the circulatingcircuit.

Then, the wafer W is cooled in the cooling portion 12b, and then achemically amplified resist is applied to the wafer W, in the resistcoating units 15a and 15b (step S8). After the pre-baking step S2, thereflection preventive resist may be applied to the wafer W (step S6)followed by baking the wafer W in accordance with the predeterminedrecipe (step S7). After the baking step S7 has been performed, thechemically amplified resist is further applied onto the reflectionpreventive film (step S8). In the resist applying steps S6 and S8, thealkaline component in supplied air is removed by the air cleaningmechanism 80 so as to lower the concentration of the alkaline componentin the processing atmosphere to be lower than 1 ppb.

After the resist has been applied, the wafer W is again baked in thebaking unit 13 (step S9). After the wafer W has been cooled in thecooling unit 12b, the wafer W is brought to the interface section 30 toalign the position of the wafer W on the holder 31. Then, the wafer W isintroduced into the exposing section 40 so as to be subjected to theexposing process (step S10).

After the exposing process has been performed, the wafer W is introducedinto the baking unit 21 of the developing section 20 through theinterface section 30 so as to be pre-baked before the developing processis performed (step S1). Then, the wafer W is developed in the developingunit 22 (step S12). Also the concentration of the alkaline component inthe developing atmosphere is adjusted to be lower than 1 ppb by the aircleaning mechanism 80. After the developing process has been performed,the wafer W is post-baked in the baking unit 21 so that the sequentialresist process is completed (step S13). The processed wafer W is movedto the cassette station 4 by the main conveying machine 6 so as to beplaced on the holder 3. The wafer moving mechanism 2 accommodates theprocessed wafer W in the second cassette 1b. The processed wafer W is,while being accommodated in the second cassette 1b, taken out from thecassette station 4.

As shown in FIG. 3B, the concentration of the alkaline component in theprocessing atmosphere is detected by the alkaline concentration analyzer50 and the results of the detection are, in real time, displayed on thescreen of the monitor 70 (step S14). If the chemical filter 85deteriorates after it has been used for a long time and the performancefor removing the alkaline component has deteriorated, the concentrationof the alkaline component in the processing atmosphere is graduallyraised.

The CPU 60 compares the detected concentration of the alkaline componentin the processing atmosphere and the threshold value (1 ppb) with eachother. If the detected level is lower than the threshold value (1 ppb),the foregoing steps S1 to S13 are repeated (step S15). If the detectedconcentration of the alkaline component is higher than the thresholdvalue (1 ppb), the CPU 60 issues a command to the alarm system 71 toissue an alarm (steps S15 and S16).

When the operator recognizes abnormal concentration of the alkalinecomponent in the processing atmosphere in accordance with the alarmissued from the alarm system 71 and/or the screen of the monitor 70, theoperator selects any one of the following methods (1), (2) and (3).

(1) A first method in which all of the processing operations areimmediately interrupted (step S17), and the chemical filter 85 ischanged (step S18). Then, the process is restarted (step S19).

(2) A second method in which the operations of the resist coatingsection 10 and the developing section 20 for processing the wafer W areinterrupted. Moreover, the operations of the other processing sections11, 12, 13, 14 and 40 for processing the non-processed wafer W arecompleted. Then, all of the processing operations are interrupted (stepS17), and then the chemical filter 85 is changed (step S18). Then, theprocess is restarted (step S19).

(3) A third method in which the operations for processing all of thewafer W (including the non-processed wafer W in the first cassette 1a ofthe cassette station 4) in the resist processing system are completed.Then, all of the processing operations are interrupted (step S17), andthen the chemical filter 85 is changed (step S18). Then, the process isrestarted (step S19).

The first method (1) enables the wafer W to be quickly and reliablyprotected from being damaged by the alkaline component in theatmosphere. However, since the wafer W, which is being processed in theprocessing sections 10 and 20, is collectively restored, the processinvolves waste.

The second method (2), in which the wafer W, which is being processed inthe processing sections 10 and 20, and the introduced non-processedwafer W are processed, enables the waste in the process to be prevented.

The third method (3) is able to further prevent waste in the process ascompared with the second method (2). However, since a long time isrequired to interrupt the processing operation, there is a risk that thewafer W is damaged by the alkaline component in the atmosphere.

As described above, each of the first to third methods (1), (2) and (3)has its merits and demerits. In order to protect the wafer W from beingdamaged with the second method (2) or the third method (3), thethreshold value of the concentration of the alkaline component in theprocessing atmosphere may be lowered from 1 ppb to 0.7 ppb.

As shown in FIG. 4, a structure may be employed in which, for example,five resist processing systems are included in single clean room 90; andthe atmospheres of the processing sections 10, 20 and 30 of the fiveresist processing systems are, in parallel, controlled by using thecommon alkaline component concentration analyzer 50, the CPU 60, themonitor 70 and the alarm system 71.

Since the threshold value of the concentration of the alkaline componentin the atmosphere in the coating section 10, the developing section 20and the interface section 30 and that in the atmosphere in the cleanroom 90 are, in this case, different from each other, the CPU 60controls the system to be adaptable to the difference. For example, thethreshold value of the concentration of the alkaline component in theformer sections 10, 20, 30 is made to be 1 ppb and the threshold valueof the concentration of the alkaline component in the latter section ismade to be 10 ppb. By detecting the concentration of the alkalinecomponent in the clean room 90 as well as detecting the concentration ofthe alkaline component in the resist processing system, the life-time ofthe chemical filter 85 can be predicted.

When the wafer applied with the resist and exposed to light was allowedto stand in an atmosphere containing ammonia at a concentration of about1 ppb and an atmosphere containing ammonia at a concentration of about10 ppb, a required width of lines of the pattern of ±0.3% was satisfiedin the former atmosphere (alkaline concentration of 1 ppb). However, thepattern was deformed excessively in the latter atmosphere (alkalineconcentration of 10 ppb).

The threshold value of the concentration of the alkaline component inthe processing units 10 and 20 and the threshold value of theconcentration of the alkaline component in the interface section 30 maybe different from each other even in the same system.

Since the alkaline component is generated in the pre-baking step S11after the exposing step S10 has been performed, it is preferable thatthe concentration of the alkaline component in the processing atmospherebe detected at least from the resist coating step S8 to the developingstep S12.

The concentration of the alkaline component may be detected at aposition near a door (not shown) in the system.

Although the foregoing embodiment has been described as a structure inwhich the present invention is applied to the system for coating anddeveloping resist for a semiconductor wafer, the present invention maybe applied when resist is applied to a glass substrate for a LCD and theresist is developed.

According to the present invention, the concentration of the alkalinecomponent in the processing atmosphere can be online-detected and theprocessing atmosphere for the substrate can quickly be improved inaccordance with the detected value. Therefore, the manufacturing yieldand the reliability of the apparatus can be improved.

Since the concentration of the alkaline component in the processingatmosphere is always monitored, the operator is able to predict the timeat which the chemical filter must be changed and the life-time of thefilter.

If the detected level of the concentration of the alkaline component inthe processing atmosphere exceeds a threshold value, this fact isnotified to the operator by the alarm system. Therefore, the operator isable to quickly take a countermeasure against the problem. Thus, thedamage of the chemically amplified resist applied to wafer W can beprevented.

Moreover, if the detected levels of the concentrations of the alkalinecomponents respectively detected in the coating section 10, thedeveloping section 20 and the interface section 30 are different fromone another after the recipe has been changed, the operator is able toanalyze the state of the problem to detect the cause of the problem.

Referring to FIGS. 5 to 9, another embodiment of the present inventionwill now be described.

As shown in FIG. 6, a resist processing system according to thisembodiment has a processing section 202, a loading/unloading section 221and an interface section 222. An exposing portion (not shown) isconnected to the interface section 222. The system is covered with acover 206. The cover 206 has, in the upper portion, an air inlet opening260. The air inlet opening 260 has three filter units 207. Moreover,openings for introducing a wafer are formed in the front and rearportions of the cover 206.

Punching metal plates or gratings are disposed on the floors of theprocessing section 202, the loading/unloading section 221 and theinterface section 222. Downflow air is arranged to flow from an upperfilter unit 207 to pass through the processing space so as to beintroduced into a position below the floor.

As shown in FIG. 5, the filter units 207 are surrounded by a case 272and attached to the upper portion of the processing section 202. Theouter case 272 accommodates a fan 262, a first filter portion 261 and asecond filter portion 263. The first filter portion 261 is formedadjacent to the upper air inlet opening 260, while the second filterportion 263 is formed adjacent to the lower air inlet opening 260. Thefan 262 is disposed between the first filter portion 261 and the secondfilter portion 263. Supplied air 280 is, through a common duct (notshown) of the plant, introduced into the first filter portion 261 in adirection indicated by arrows shown in FIGS. 8 and 9 to be allowed topass through the upper first filter element 270. Then, supplied air 280is allowed to pass through the lower fan 262 and the second filterelement 271.

The second filter portion 263 acts to remove particles from supplied airand has a filter element in the form of a sheet made of glass fiber.

It is preferable that a gasket 274 be made of a material which does notconsiderably generate ammonia. For example, it is preferable thatsilicon rubber or PVC be employed. When the gasket 274 was submerged ina very pure water to measure the quantity of elution, a quantity of 20ng/cm2 was detected. If the quantity of elution of ammonia is theforegoing level, it can be said that the gasket 274 does notsubstantially generate ammonia in the atmosphere.

As shown in FIG. 7, the processing section 202 has, in the centralportion thereof, a conveyance passage 231 extending in the direction ofthe X axis from an end 261 to another end 262. A main conveyance machine203 is disposed so as to be capable of traveling along the conveyancepassage 231. The main conveyance machine 203 has an arm for holding andmoving the wafer W. The conveyance arm is able to move in the directionsof the X, Y and Z axes. Moreover, the conveyance arm is able to rotatearound the Z axis by an angular degree of θ.

An adhesion unit 204, a resist coating unit 251, a heating unit 252, acooling unit 253 and a developing unit 254 are disposed on the two sidesof the conveyance passage 231.

Referring to FIGS. 8 and 9, the upper first filter portion 261 will nowbe described.

The first filter portion 261 has filter elements 270 and 271 stackedvertically. Supplied air 280 is initially allowed to pass through thefirst filter element 270, and then allowed to pass through the secondfilter element 271.

Each of the first and second elements 270 and 271 is in the form ofbellows made of a sheet, that is, projections 270a and 271a and recesses270b and 271b are alternately repeated when viewed from supplied air 280so as to be formed into a pleated shape. The recesses 271b of the secondelement are formed in the downstream portion of the projections 270a ofthe first element, while the projections 271a of the second element areformed in the downstream portion of the recesses 270b of the firstelement.

Each of the elements 270 and 271 has a slit 273 through which airpasses. The slit 273 of the first filter element 270 is formed in theupstream projection 270a, while the slit 273 of the second filterelement 271 is formed in the downstream recess 271b. The side portion ofthe second filter element 271 is, through a seal layer 272a, attached toa support frame 272.

The first and second elements 270 and 271 have substantially the samesize. For example, length L1 in the direction in which air flows is madeto be about 70 mm, bending interval L2 is made to be a pitch of about 4mm, and the gap L3 is made to be about 5 mm or less. A gasket 274 isattached to a support frame 272 adjacent to the air outlet opening. Eachof the first and second elements 270 and 271 is made of a carbon fibersheet or an olefin fiber sheet. The foregoing fiber sheet is impregnatedwith phosphoric acid solution.

A method of manufacturing the first and second elements 270 and 271 willnow be described.

Initially, the fiber sheet is submerged in phosphoric acid solution, andthen the fiber sheet is set to a centrifugal separator so as tocentrifugally separate and remove an excessive amount of the phosphoricacid solution. Then, the fiber sheet is pressed so as to be formed intoa plate form. As a result of the pressing operation above, theconcentration of small pores in the fiber sheet can be raised so thatthe shapes of the small pores are uniform. Thus, the small pores arearranged regularly and the specific surface area can be enlarged.

As expressed by the formula (1) below, the ammonia component in suppliedair 280 reacts with phosphoric acid contained in the first and secondelements 270 and 271 and thus is captured. When supplied air 280 haspassed through the first filter portion 261, the concentration ofammonia is finally lowered to a level of about 0.1 ppb. ##STR1##

Although the performance of the first filter element 270 for removingammonia deteriorates gradually due to use for a long time, the wantingof the removal performance of the first filter element 270 can becompensated by the second filter element 271

Consumption of phosphoric acid takes place in the order as theprojection 270a of the first element, the recess 271b of the secondelement, the recess 270b of the first element and the projection 271a ofthe second element. Note that the differential of the consumption rateof the phosphoric acid between the projection 271a and the recess 271bis small. Therefore, the synergistic effect of the difference in theconsumption rate of the phosphoric acid between the two portions and thedifference in the start timing for the consumption of the phosphoricacid between the same reduces the scattering of the quantity of theconsumption of the phosphoric acid between the projection 271a and therecess 271b. As a result, the second filter element 271 is uniformlyaged and the life of the second filter element 271 is longer than thatof the first filter element 270.

When the first filter portion 261 is changed, the first and second firstfilter elements 270 and 271 may be changed simultaneously. As analternative to this, the second filter element 271, which is able towork, may be allowed to be retained and only the first filter element270 may be changed.

As described above, according to this embodiment, the life-time of thechemical filter can significantly be elongated. Therefore, thefrequency, at which the filter must be changed, can be lowered.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. A resist processing apparatus having a processingregion and a non-processing region which are air-conditioned, saidresist processing apparatus comprising:a resist coating portion forcoating the resist with a substrate; a heating portion for heating thesubstrate subjected to an exposing process; a cooling portion forcooling the substrate; a developing portion for developing thesubstrate; an interface portion for transferring/receiving the substratewhich has been subjected to the exposing process; means for transferringthe substrate between said interface portion and each of said resistcoating portion, said heating portion, said cooling portion and saiddeveloping portion; means for supplying downflow air to said processingregion; filter means disposed in a predetermined position with respectto said processing region and arranged to remove an alkaline componentcontained in downflow air to be introduced into said processing region,said filter means having an element containing an acid component forreacting with the alkaline component to capture the alkaline component;concentration detection mean for detecting the concentration of analkaline component existing in at least one atmosphere in said resistcoating portion, said developing portion, said heating portion, saidcooling portion and said interface portion; means for setting athreshold value of the concentration of the alkaline component in theprocessing atmosphere which causes defective resolution of the resist;and display means for displaying a value detected by said concentrationdetection means.
 2. An apparatus according to claim 1, whereinsaidconcentration detection means is a concentration analyzer for solvingsample air sampled from said resist coating portion, said developingportion, said heating portion, said cooling portion and said interfaceportion in pure water to detect the concentration of the alkalinecomponent contained in said sample air.
 3. An apparatus according toclaim 1, whereinsaid filter means has a first filter element and asecond filter element disposed vertically and disposed such thatsupplied air is allowed to pass through said first filter element andthen allowed to pass through said second filter element.
 4. An apparatusaccording to claim 3, whereinsaid first and second filter elements havea pleated shape formed by bending a sheet to be in the form of bellowsand having projections and recesses repeated alternately when viewedfrom a direction in which air is supplied.
 5. An apparatus according toclaim 4, whereinthe recesses of said second filter element are disposeddownstream from the projections of said first filter element, and theprojections of said second filter element are disposed downstream of therecesses of said first filter element.
 6. A resist processing apparatushaving a processing region and a non-processing region which areair-conditioned, said resist processing apparatus comprising:a resistcoating portion for coating the resist with the substrate; a heatingportion for heating the substrate subjected to an exposing process; acooling portion for cooling the substrate; a developing portion fordeveloping the substrate; an interface portion fortransferring/receiving the substrate which has been subjected to theexposing process; means for transferring the substrate between saidinterface portion and each of said resist coating portion, said heatingportion, said cooling portion and said developing portion; means forsupplying downflow air to said processing region; filter means disposedin a predetermined position with respect to said processing region andarranged to remove an alkaline component contained in downflow air to beintroduced into said processing region; means for setting a thresholdvalue of the concentration of the alkaline component in the processingatmosphere which causes defective resolution of the resist; firstconcentration detection means for detecting the concentration of thealkaline component existing in at least one atmosphere of said resistcoating portion, said developing portion, said heating portion, saidcooling portion and said interface portion; second concentrationdetection means for detecting the concentration of the alkalinecomponent existing in the atmosphere of an external environment ofresist processing system; and display means for displaying valuesdetected by said first and second concentration detection means.
 7. Anapparatus according to claim 6, whereinsaid concentration detectionmeans solves sample air sampled from said resist coating portion, saiddeveloping portion, said heating portion, said cooling portion and saidinterface portion to detect the concentration of the alkaline componentcontained in sample air.
 8. An apparatus according to claim 6,whereinsaid filter means has first and second filter elements disposedvertically and disposed in such a manner that supplied air is allowed topass through said first filter element and then allowed to pass throughsaid second filter element.
 9. An apparatus according to claim 8,whereinsaid first and second filter elements have a pleated shape formedby bending a sheet to be in the form of bellows and have projections andrecesses repeated when viewed from a direction in which air is supplied.10. An apparatus according to claim 9, whereinthe recesses of saidsecond filter element are disposed downstream from the projections ofsaid first filter element, and the projections of said second filterelement are disposed downstream of the recesses of said first filterelement.
 11. An apparatus according to one of claims 2 and 7, whereinthe concentration analyzer is an ion chromatography.
 12. An apparatusaccording to one of claims 1 and 6, wherein the display means isprovided remote from said processing region, thereby constituting aremote monitoring system.
 13. An apparatus according to one of claims 1and 6, wherein each of said first and second filter elements is formedof a fiber sheet which is pressed, after the fiber sheet is submerged inphosphoric acid solution such that an amount of the phosphoric acid isimpregnated into the fiber sheet, and then is rotated at a high speedsuch that an excessive amount of the phosphoric acid solution iscentrifugally separated and removed from the fiber sheet.
 14. Anapparatus according to claim 13, wherein the fiber sheet is formed of aglass fiber.
 15. An apparatus according to one of claims 1 and 6,wherein said filter means includes a gasket formed of one of siliconrubber and vinyl chloride.
 16. An apparatus according to one of claims 1and 6, wherein said setting means sets the threshold value such that thethreshold value differs from a threshold value in said non-processingregion.
 17. An apparatus according to claim 16, wherein saidnon-processing region is the interface portion.